HD 29399 b
HD 29399 b is a cold gas giant orbiting the K1 III star HD 29399 in the constellation Reticulum. It lies about 144 light-years from Earth and was discovered in 2022 using the radial velocity method.
Is HD 29399 b in the Habitable Zone?
HD 29399 b orbits inside the inner edge of the habitable zone of HD 29399. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 29399: 2.500–6.082 AU (conservative: 3.166–5.766 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Orbit and Year Length
A year on HD 29399 b — one full orbit around HD 29399 — lasts 892.7 Earth days, longer than an Earth year. It orbits at an average distance of 1.913 AU. Its orbit is mildly elliptical (eccentricity 0.05).
How Was HD 29399 b Discovered?
HD 29399 b was discovered in 2022 using the radial velocity method, with observations from La Silla Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is HD 29399 b?
HD 29399 b is 144.0 light-years (44.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1882. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,534,400 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. HD 29399 b scores 0.31, ranking #1,206 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 29399
HD 29399
- Spectral type
- K1 III
- Surface temperature
- 4,845 K (Sun: 5,772 K)
- Mass
- 1.17 M☉
- Radius
- 4.50 R☉
- Luminosity
- 10.0399 L☉
- Age
- 6.2 billion years (Sun: 4.6)
Planetary System
HD 29399 b is the only planet known to orbit HD 29399 so far.
HD 29399 b — Complete Data
| Mass (best estimate) | 498.99 Earth masses |
|---|---|
| Orbital period | 892.70 days |
| Orbital distance | 1.913 AU |
| Eccentricity | 0.050 |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 144.0 light-years (44.2 parsecs) |
| Constellation | Reticulum |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2021-11-18. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 29399 b
Is HD 29399 b habitable?
No — HD 29399 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 29399 b?
HD 29399 b is about 144 light-years from Earth in the constellation Reticulum. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,534,400 years to get there.
How long is a year on HD 29399 b?
One orbit around HD 29399 takes 892.7 Earth days.
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